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DMIC Report 158

SW*=.)er 15, 1961

0O

-• STRESS-CORROSION CRACKING OF

"HIGH-STRENGTH STAINLESS STEELS

IN ATMOSPHERIC ENVIRONMENTS

DEFENSE METALS INFORMATION CENTER

Battelle MemoTial institute

Coalmlb 1, Ohio

S. .. , • , , n nn nn n • Imm nu I I Iu I I lmm

DN[C Report 15-3

STRES,-COROSION CRACK-MG OFIGH-STtRE--NGTH STAiLEl STEELSIV iATO110S PillERI UC EINV1R 0 'N I LS

C- 3- S1ider

OFFICz OF THE DIRECTOR OF D-_.r F±.r'ZRESEARCH -AZ-D ENGUEERUG

DEFENSE METALS INFOR•4ATION CENTERBa•-ele Memoral institate

Columbus 1. Ohio

TABLE OF COLTE=-%Ts

=laze

S - T - - - - - - - - - - - - - - I

DU!OM3C-7!---- - -- ------------------------------------- -- ------------ 3

TLC -------------------------------------------------------

Maials Tested --43Let-bod o~f Szressi= -- - - - - - - - - -Pzepara:E of Test Speci~c~s --Test --e~ -

- - - - - - - --L - - - - - -

coazd-RGrild A S=I-Iess ste-Is 8SePe:p&--de~gaie S:,-Iexj -e~ - 9

S~ess-c*o(-oe -Res=lts fo !7-7 PS - - - 7S-rs Ris .s.-Js f= PH. !5-7 W. M ----- 20

St-e3ss-rrz! PRZI±s fO! AM 3SO a~d At .55 - ±6 ---- znarte==tic jm~d Ms~~ ~• -i~eS~a-ess &~ecls ----- 30

Dis-S O or- RELS*-- - - - - - - - - - - - - - - - - - - - - - 35S

WORK M PRa R K- -- --- - - -- - - 3?

- - - - -- - - - - - - - - - - - -8

STRESS-CORROSION CRACKING OF HIGH-STRENGTHSTAINLX.SS STEELS IN

ATMOSPHERIC ENVIRONMENTS

SUMMARY

The application of high-strength steels in the construction of aircraftand missiles has created a further demand for information on the stress-corrosion properties of such steels. Several experimental programs dc-signed to develop such data have been in progress for the last few years.

In this report, the available information on the stress-corrosion crackingof the high-strength stainless steels has been assembled and tabulated ac-cording to alloy type and to the environments to which they were ,xposed.The stainless steels, for which some data are a-ailable, include the cold-rolled austenitics, the martensitic grades, the martensitic precipitation-hardenable grades, and the semiaustenitic precipitation hardenable grades.Exposures were in the marine atmosphcre at Kure Beach, outdoors at sev-eral semiindustrial locations, and in several laboratory test environments.

Data on the chemical analyses, heat treatments, and mechanical propertiesof the test materials are included.

All of the data compiled in this report were obtained on bent-beamspecimens stressed below the yield point.

Many factors are known to influence the stress-corrosion cracking ofmetals. These include composition of the alloy, heat treatment, metallur-gical structure, preparation of the test specimens, stress levels, and theenviroaLanaktal conditions. Insufficieut diht&ame been accumulated topermit quantitative comparisons of the alloys discussed in this report, andmuch of the information is considered preliminary because the tests arestill in progress; however, tentative conclusions can be made abu,.. che uti-lization of these steels. The compiled data also indicate where additional

testing and refinements in the procedures are needed +o get more reproduc-ible and reliable results.

Cold-worked and stress-relieved austenitic stainless steels such asAISI 301 have shown excellent resistance to stress-corrosion cracking inboth marine and laboratory-type exposures. This is true on specimensstressed to over 200,000 psi. The good performance is attributed to thefact that high strength is developed by mechanical working, r"thcr than byheat treatments.

In the 17-7 PH and PH 15-7 Mo tests also, the most resistant speci-mens were those in the CH 900 condition; that is, the cold-rolled and tem-

pezed structure. These alloys in the other conditions were shown to be

su~cepih'e to s~rcs-corrosion •crackinv i, a marme attnosphere when

stressed to ncvr 50 per cent of the yield str*-en-.h. .!-ct.c-.: sutce&,GibAity

wa5 not related solely to the strength of the alloy but was also deter-minedby the heat treatment used to de-dlop the properties-. n general, the heattreatments that developed the stronsgest alloys also resuilted in greatersusceo=ibil•y to stress-corr, _- ion cracking' both allovs, in certaincases, there w-tre harge differences in exposure tim.es bet%-een toose spc-i-

mens that failed and those that did not fail. No fai-.res were reported o=

these alloys (17-7 PH and Pil 15-7 Mo) exposed to semnindustrial

atxanosL-neres.

The data for A.M 350 and AM 355 are not very extensive,. The CRTand SCCRT conditions developed very high strengths, ._nd ir-unty fromcracking at Kure Beach was obtained only on sp.ecimens stressed to less

50 _er cent of their yield strength. in the salt-spray exposure, speci-mnens cut transverse to the rniling direct!o -ere strongly susceptible,-r-"-reas those cu-t longitud-nally did not crack. More -,&or'k is need-d on this

po.in. The SCT 850 cendition was shown to be oo-ar susceptible to craclkingwzn-- was the CRT 850 condition in the at--osrnneric exposure tests. "D..ffer-

ences were also ...oied in res-,ts on different heats in the CR.T 850 conditicn.Perhaps. the two CIRT 850 conditions did not have ecual a•.-ounts of coldreduction.

.e:' data are zi'Ven for 17-4 PH in 6hect zfin ex-sed for za•leost ayear at Kure Beach.. No failures occurred -n sp •-cir-ens in the H 900 con-dition I-ield strength 180.000 psi) stressed vý to S0 per cent of the yieldstrength. Welded sp-cimn.s inn the H 9-0 cL--dition -ailed, .and a solution-heat treatanent following the welding did not completely rC1ore the immunityto se-crro = crac.in. Specimens aged at 1025 F or higher have notfailed-. The tests are stili in progres " and zno-e data sl=-•ud be forthcoring.

Allov-: 12 MoV and Stainless W were ,.ormed to be cuite susceptible

to . .. u. f u~n crac-ing, wi" the later Deing Olightly su-erior. Highertemoering temperatures for 12 MoV reduced the !ssceptibliuty to a--g,at the sane .- e causing a com-siderale reduction in the strength ef thealloy.

1*

3

UNTRODUCTION

The generali features of stress-corrosion cracking were sunrnmarizeain a recent DMIC rer~ort(l)* to prcwidc a bac'kground for xmateritals and desigynengineers an-d for others inolved in the use of high-strength steels. Aly

ii nx.!ry :aet= _.stexns, both ferrous and nonferrous, are suscewtible tostress-corrosion cracdn in specific environments. This does not neces-sarily prevent the use of suchn metals and alloys but indicates that certainprecailtions should be taken to avoid faiures in service. The successfulutilizatior. of any metal- is dependent, therefore, on adequate considerationof sti-ess'-corrosion n-rope rties, as well as of its other properties. This ipartictuIariy irur for the high-strenngth steels in aircraft and missilear-lications..

The faLtors that vinflucn-ce or contribute to stress-corrosion c.-ackxngmay- arise im cn or all of the steeps and sequences that the metall encountersin being conrertcd xrorn its original to its final form.. Heat treatment,quenching. fabrication, welding and other assembly operations, surface fin-ishing, and other production steps may affect either the metal-urgica -1 uctaire zand mechanical. orooerties o.f the alloy, or result in the develoninent. lharmiful residual stresses in the finished product.. The alloys are exnooselato a variety of conditions during these operations, and it is important to con-s-der what their effect will be on the stress-corrosion-cracking propertiesaf th~e.materials. Then there are the conditions prevailing during- trans-pt-rtation and storage of the finished aircraft or missiles. Careless hanndlizgm-av result in deforrnat:o or surface damage which aggravates stress-corrosion cracking of susceptible materials by introducing additionall stressesand providing sites fý,r the start of corrosion. Finally, aircraft and missileszre subjected to a -rariety of environments in o~peration-. Exnosure to cycli-cwetting and di-ying, in humid or salt air locations, and lacri-xime undergroundstorage a-e ex.ainples of possible harmitut c=ndi~tions for susceptiblematerials.

th.e increasing use of th-e high_--strength steels in the constru-ction %,faircraft and niissiles within the past few vears resulted in the initi4aticni ofseveral test programs designed to provide data on the s.~ress-corrosion s-us-ceptibility of such steels. The steels of intere~zt in the high-strength cate-glory miay be classified as

(1 Stainiess steels(2) Hot-work. die steels(3) Low-alloy engineering steels.

The first of these may be broken down furtOher to include the maztensilicstainless steels, the zuartensitic and seminaustenitic precipitation hardenablestainless steels, and the cold-rolled auste.nitic stainless ste-els. Some data

4

on stress-ctrto5:in cracking have bec-rn.e -a,'ilablc as a re:uh of the test?rvrerams mentioned above, but not all cf this information has t-een b.....i- z ;hv ±iu±cal -..--rnaas. Furthermore, differences in materials and in de-tails tf !ihe tests rakc cvaluation of scattered data difficult.

The purpose of this report is to present a compilation of data accumu-lated on the stress-corrosion cracking of hi-gh-strength sraiiless steels inlab-oratory and atmospheric environments. Also, information concerningheat treatments, mechanical properties, and test procedures is included.It is not always Dossiole to make unqualified, quantitative comparis,;nswhere so many factors ma; :n-fluerzcc test results. 7 he data tabulated inthis report, therefore, are intended to help in the selection of materialsfor use in aircraft and mii-le applications rather than to predict the per-formance of the materials under service conditions. The data were assem-bled from tests conducted by the U. S. Steel Corporation, ArrMco SteelCorporation, Allegheny Ludlamn Steel Corporation, anrd the .OrhAviation Corporation at Los Argeles. So-ne of these tests are still in prog-ress, and additional data from these and other test programs could be in-cluded i-r supplements to this reporr to hri-ng zhe information un to e-da-_.

EXPERLMENTAL DETA-iLS

Materipas Tested

Twelve stainless steels of four tv%-pes were investigated:

(1) Mar:ensitcUSS !z MoVl

"(Lar Mtrensizic orecipitation nardenable17-4 PH

Stainless W

(3) Serniaustenitic Drecip;tation hardenable17-7 P-HPH 15-7 Mo-AM 350

35.' 5

(4) Cold-rolled austenitic.aISi 30!AISI 20 1

AISI z2zUSS TenelonrUSS 17-5 MnV

specimens. U. S. Steel and Armco used a rigid stainless steel bar withsicts machined in it, spaced for either a 4- or 7-inch span. Specimens cutto some length greater than the span between the slets can be stressed byplacing one end in one of the slots and bending into a simple arc just enou;hto s, the other cnd in the opposite slot (see Figure la). The exact speci-men length needed to produce the desired tensile stress in the outer ngersat the -iddle of the specimern is determined from a relationshin between thestrain, the specimen length and thickness, and the span between the slets inthe s ecimen- holder.

3% ort A-ne an. -Aviation used toe same principle, but t:e fixture con-sisted of two ilo-tzed blocks' of an epox.--glass larninatc held in place by a boltand nut. The desired stress level was !'tained on one specimen of eachgroup by adj;usting the distance berwein -h-e end blocks -With the bolt and nuLThe strain on the bent specimen was determined from strain-gage measure-ments. Then the deflection of the siecimnen was measured, and this valuewas used to reproduce the same bending and stress levels in other speci-mens of the group. Protective coatings were applied to the fixtures.

In the Allegheny Ludlum tests, the strip specimens were bent over acenter support in the test assembly. The specimens were bent by tighteningthe bolts and nuts at the ends of the jig until the desired strain, measuredby a strain gage, was produced at the center of the specimens. Each speci-men was insulated from the jig assembly by Teflon tape and washers. Thisfixture is illustrated in Figure ib.

Preparation -.f Test .jnz•ý;.ens

Many factors are known to affect the reproducibility oi •tress .c..rrosiontest results. One of these is the condition of the specime=n =- the start of thetests. In all of the programs reported, an effort was made to prepare speci-mens carefully and reproducibly, with a uniform and clean s.rface. so as tomninimize erratic corrosion results caused by variable surface zinditions.There were some differences, however, in the actual steps taken to preparethe test specimens. The procedures used are given below.

U. S. Steel

(I) Specimens sheared from sheet stock to proper -i-th. butlonger than used in the tests

(-) Heat-treated to get the desired properties(3) Surfaces ground on S0-grit dry cmery belt to remove scale

and visible surface defects

a. Fixture-'- ~'d by U. S. Stpee1 Armco, anzd,in bi-~nl n Nonrth Aii-erican-

b. z nree-noint loadin~g fixtu re used by

FITGURE I-. TE-ST IFIXTUR-ES

7

(-4) Gro;nd on I20-grit emery i"'?(5) Cut v.- length toproduce tize desired stress afttur bendingit.! Dcogrias.A in tr.-chlorethylvene vapor(-;I Vwashe-d in distilled water(8) Rinsed in act-tone(9) Stcred! in desicc.,tor untill put in test.

Arince

'!) SDeccirens cut iromn sheet stock(2) Machined and deburrp-d,3) Cleaned i;!- inhiib-ited p osp.'ore- acid(4) Rinsed in distilled water(5) Heat treated to des:red properties(6) Destcaled by wet gri: ;-last io a curface rougglmcss of

' :5- (s mic r~z.iches rms..

r:o..oih American Avi.ation

(i) Specimens sheared oversize ( i-l11 x 8- 1 !A iur-r-ies's()Alkaline cleaned and coated with a scale -inhibi-ting co~m-

ooxa-nd Prior to beat treat-nent(3) Heat treated(4) Machined to I1-000 -0. 00 1 x 8. COO *0. 00 1 inches(5) Liquid honed(6) Passivated by. immersion -- 4v per cent nitric acid for

I hour at room termoerature.

Aileg-heny LuAditin

(1) Specimens shear&.d from sheet in the desired condition.,to a size suitable for m.ountinr in. the jigs

(2) Machined *-- cli.--iinate edge shezar effects1.3) Tempering scale removed by -picklI.ing in cold dilute

nitric -hvdrofluoric. acid solution.

In the program.-s where the svecilnens were bent into the jigs by hanmd,ti-e spec imens were handled with clean canvas gloves to avoid contamin-ationir.z~m fingerpr~n~tc, or other sources. No dai.a are available that lvcrmiteivaluatior. of the preparatory systems listed above.

V

Test Environments 2

Sal't air, rntarinc-atmosphere exposure in the U. S. Steel, Armco, andAllegheny .Ludlum programs wpre conducted at the 80- and 800-foot lots(distance trom ocean) at Kure Beach, North Carolina. The North American-aiti-= speci.-ens were exposed in Z0 per cent salz fog t 95 3 F ac-

cording to Federal Test Method Standard--,-ea, and n:- a cyclic h'midityrest, MI-L-E-5272 C, t- simulate a-i extreme tropical climhate. The delails-of -hc ,±auer exposure are given in the tables of test results later in the re-port. Aulegheny Ludluni also exposed specimens n a 20 per ent neutraisalt spra•. Some speci-mes in all four programs were exposed to the out-door atmospheres existi.g at ,he ccmpany locations. namely, Monroevilleand Brackenridge, Pe.nnsVIvania, Los Angeles, Calfornia, and Middietown,Ohio. The conditions Arere described as beLng mild to s "m"d'_--•-

RESULTS

The accurnIUjated data for each class oi alloys from a- ,f the sourcesreviewed .2 been assembled into tabular form to facilitate comoarison and&.s-.ussion. The data includc chemical comvosition of the alloys, their heattreatment an imechamical proper-Lies, exposure conditions, and results. Afew blank soaces in the tables indicate that the information was not reportedin the original sources. Also, since the tests were conducted by four differ-ent comp anies, there were so=e scattered data rerorted that did not fallreadily under the tabie headings. Th.ese were i--cluded as- footnotes to thetables.

Cold-Rolled Austez-dtic Sta.-ess Steels

The cold-rolled austenitic ; =-------------::. • .. u= z-

perature, and frequently contain small ai•!o_--s of delta ferrite. Verz- highstrengths may be developed during cold rolling, by a com:-ination of workhardening and tran.sformnation of the austenite to marteansite. Usually astress-relieving treat-ment is used -,o develop the best combination of strengthand duczility. The chemical composition of the steels tested and the treat-ment and mechanical orooerties are given in Tables I and 2. The results ofthe stress-corrosion-crac-king experiments are in Table 3. The steels at-tained very high tensile strengths, ranging f-rom about 185,000 psi for full-hard AITSI 301, to a range of 245,G0C to 289,000 psi for the ex:ra-.--rd steels.The data in Table 3 indicate that, in gener.l, this class of steels is veryresistant to stress-corrosio= crack•dng. It is true that some of the test speci-mens were lightly stressed (less than 50 per cent of the ultimate tensilestrength), 14M- -&. Pi ul-ers were stressed at up to 70 per cent of the tensile

strength- The tests made by U. S. Steel were at 75 per cent of the yieldstrength. Only one sample in the entire group developed a crack in tfhl

ex-.r .- rc-. This cracked after 347 days at the 80-foot lot

at Kure Beach while stressed a-: 202,000 psi. Two otherr developed a crackin the laboratory alternate-inunersion test in 3-1/2 per cent salt solutivr.after 33 " ys. ¢ Duplcates did not fail in about 400 days, and it was suggested

that the two failures after only 39 days may have bpen abnormal. caused by asuozerficial nick or partice of ,.,zed-n-_• Nc•aie, if so, it emp-hesizes the needfor care in hardLing and fabricating these high-strength steels. it may alsobe noted that the three fi'lures all occurred on s:eci-mens cut trransv-rse tothe direction of roiling. There is no apparent eviden-.e to indicate whether

this is significant.

AMSZ A-S V_.I 3i 6-91~ CSI~22 1 .~ -It 2.6 -

.Aim ,.e rSS O. .C ...0_ . 0...• I.. .3 Z:. . 0.!. --

MSI-- ILIs :_Is Oa.n !6- itc e-1..1 &il 2.. 0.2: 0..35__ -__ • " v..*- • . . ,= C: •,• 4.2 -.-. #.T•

(.l) VS - L.5. s-.-,.-,~.•L- .U'IT. -' •- S C,c•.--

AM±Acat 7_4qiýv~"113-4 a01

The other alloys in this group were in the U_ S. Steel tests and had

been treated :t prod•ce yield strengths ranging from 215.00G psi to 264,0000zsz. Whon stressed at 75 per cent of their yield strength, no failures oc-

curred- during 240 ays*' exposure at Kure Beac-.

Se.niaustenitic Przcinitation-HFardenableStainless Steels

"The semiaustenitic .rccivitation-hardenable stainless steal. av.are•--•-.,i-ave rczeived more attention than the otfhers covered in this repu--z, andmore data on stress-corre.sioon-cracking data are available. The pi 2 'sical

rne'aurgy of these alloys has been well sum-..marized in DMIC Report 111. P(2As descussed in that report, the alloys have achieve•d popularity, because"hey can be fabricated easily in the annealed condition, and then hardened tohigh strength levels by a series of ther --. al treatments. The hardening mech-anisrn consists of transformation from an astenitic to a martensitic atrix,

I !''1! !!! !! ! !' !

10

Sze"

11-M -SO I CCI 2-. -Lce

_-m-+ A -IE--ac-S-==Tk.dn

AI~ ~1 A F- b~is~s:dcLre- --

AMS 301 AL. Evaf hzed. sL~r,.cn elrcd -

m ==~ ~1:2ýL. sz ctc~xC, -35_-c

=3S !:-. MaS Ezra li

-Y E USS -

(a) USS - U.S- 5%-4 C=xra=A-2 - AU :!Ix L~ce 4-- ': 2.:io:.

M'*Z . AUST&F.7I-C ST5ARIMUSS S57z=S

Time. YjC-:d L-g, Tc2:c Stm'-46.7 2 1c

2 233 2 Eori-d"

1$4 70Lcrmiwdz1

2p3

2 22~5 :!-; 2-Cozaa

- 25! 2E-3-2601 -IF&p~z~

2 -6 --

2 215 266-Lc?2

12

TABLE 3. RESULTS OF STRESS-CORROSION CRACKING TESTS

Applied Stress

Source Per Cent of

Alloy of Data(a) Condition(b) Direction Tensile Strength 1000 PSI

AISI 301 USS Extra hard, stress relieved Longitudinal 75(0 178.5

AISI 301 AL Full hard Longitudinal 10 to 70 18.2-127.4

AISI 301 AL Full hard Transverse 10 to 70 18.8-131.3

AISI 301 AL Full hard, stress relieved Longitudinal 10 to 70 18.4-128.7

AISI 301 AL Full hard, stress relieved Transverse 10 to 70 18.7-130.8

AISI 301 AL Extra hard, stress relieved Longitudinal 10 to 70 25. 9-1.61.3

AISI 301 AL Extra hard, stress relieved Transverse 10 to 70 28.9-202.2

AISI 201 USS Extra hard, ,trczs relieved Longitudinal 75(0 1-71.8

AISI 202 USS Extra hard, stress relieved Longitudinal 70A. 161.3

USS TENELON USS Extra hard, stress reUev-.d Lorngitudinal 75M0 179.3

USS 17-5 MnV USS Full hard, stress relieved Longitudinal 7 5(f) 177-198

(a) USS - U.S. Steel CorporationAL - Allegheny Ludlum Steel Corporation.

(b) See Table 2 for details.(c) 20 per cent neutral salt spray.(d) 3-1/2 per cenm NaCI solution; 10-minute immersion, 60-minute air dry cycle.(e) Only at: 70 p:,r rent of tensile strength, two specimens for each condition.(f) Per cent of yield strength.(g) One specimen stressed at 50 per cent of tensile strength cracked after 39 days.(h) One specimen stressed at 70 per cent of tensile strength cracked after 39 days.(i) One specimen stressed at 70 per cent of tensile strength cracked after 347 days.

13

ON CULD-ROLLED AUSTEMTI'C STAINLESS STEELS

Number of Days Exposure Without Failure

Number of Kure Beach, Kure Beach Alternate AtmosphereSpecimens S0-Foot Lot 800-Foot LoL Salt Spray(c) Immersion(d) Brackenridge, Pa.(e)

6 240 ........

8 398 398 419 405 3508 398 398 415 4056() 350

8 398 398 414 388 350

8 398 398 417 3 88(h) 350

8 398 398 285-391 392 3508 3980 398 344 392 350

6 240

6 240

6 240

15 370

pius soMr precipitation hardening curing aging trearments. Alloys 17-7 PH!j, PH !:;I7 IAs . -re AU.A --- l A3 +U_ -u =

a. --- =d ---

are said to harden mainly by the austenite-to-martensite transfcrm-nation _ol-lowcd by a teme rmrng heat treatmnent.

The che-mical composition of the alloys ir- this group are given inTable 4, and the deL.iils of the heat trcaLnents are in Table 5. T-he harden-ing sequence is seen t.3 include an austenite-conditioning step, during whichch-n-.nium carbides are orec•.itated crem th•e aust. -_;t-e. This results inraising the Ms tempetaturc sufficzently that trans-ormation to ma-te--site is.. re readily accomplished in the subseque=nt eperaticns. "the fmal treat-ment is the aging step, during which hardening phases are vreci-i-Aded in thealloy. The temperature and duration of the aging treatment have someeffect on the size and distributio- or the precipitate paxricles. All ef theseste-s conmbine to develop the mechanical Proverties of the heat-treated alloy.The mechlaism.s of hardening are discussed in much greater detail in thereport mentioned abo-ve. (2)

ABE CECL ý-L COC,7 crC 1- ±. CC T*.: =C ?.-• AT-P

An- - D4 C I P S S: C: N. I.... -I V Al

17-iI SA o-9.5 1 40.& 0_-4 --- Z ';_ ~i 7 I= - - - - 1

i-,l .c•9 . -- -- -.-. • -- 4.-. •-. -- -- . -

A==CM .- o

?i! MSo Z5' .712 e..C' -. 32 14. 7 6-34 i.41 0- 00Z3- 13P I-21 X&A 0070 0-6i -- .24 ;-L33 LZI1! .34-- . - LM

I .M3. '.AA 0-. 1; 0, 72--1.71..

(2) UZ - VXS.. Stec: Cn=rj-XIUL - .ve- A,~c== AL'-nk=C 1--

A. - -ie~ ~ ~C~-A=C - A=cv Sz=; Cca:?=t

(c) A-.~c d -; b-

Cold roling is also used to produce hbadening in the alloys 2f thisgroup. This causes the austenite to transfor.m to martensite, and the alloy;s theu aged or tema-red to develop the final properties. -Alloys i- .heCl 900 and SCCRT conditions Itave very 14gh tensile and yield strengths, '-1-it should be noted that their ductility is low. The properties of all of the al-loys tested in the group are lsted in Table 6.

_I_= _ ; _ _I i! II ! ' i

15

!-AniF s. IFAT TRFATMFIT OF TtI-F SFMIATISTFNITIT PRCIPTITATION-HARDENABLE STAINLESS STEELS

Austenite Conditio;1ing Ae, or TemperSource of Tempcrature. Time, Temperature. Time.

Alloy Condinton Data(a) F minuLes Tramformation F hours

1I -'l PH TH IiUb USS 140U VU Cool to 60 F within I hr, hold 30 mi,, 100b 1-1/2TH 950 USS 1400 90 Cool to 60 F within 1 hr. hold 30 miin 950 1-1/2Rli 950 USS 1750 10 Hold 8 hr at -100 F 950 1

Ti! 1075 NAA 1400 90 Cool to 32-60 F within 1 hr. hold 30 min I '.5 1-1/2TH 051) Armco 1400 90 Cool to 60 F within 1 hi. hold 30 mrin 1050 1-1/,PH 950 Arnco 1750 10 Hold 8 hr at -100 F 950 1CH 900 Armco ..-- Cold rolled at mill 900 1

PH 15-7 Mo TH 1050 USS 1400 90 (ool to 60 F within I hr, hold 30 rini 1050 1-1/2RH 950 USS 1750 10 Hold 8 hr at -100 F 950 1RH 950 NAA 1750 20 Hold 5 hr at -110 F 950 1BCHT(b) NAA 1625 20 Cool to 1000 F in 45 min, air cool to 900 8

room temp.. 5 hr at -100 FTH 1050 Armco 1400 90 Cool to 60 F within 1 hr. hold 30 min 1050 1-1/2

RH 950 Armco 1750 10 Hold 8 hr at -100 F 95G 1

CH 900 Armco ..-- Cold rolled at mill 900 1

bCH"Ti) Armco 1675 20 Cool to 1000 F in 45 min. cool to room

temp. 8 hr at -100 F 9i0 24

AM 350 SCT 850 NAA 1710 20 3 hr at -110 F 850 3BCHT(b) NA A !675 20 Cool to 1000 F in 45 min. cool to room 900 24

tcmp. S hr at -100 F

AM 355 SCT 850 NAA 1710 20 3 hr at -110 F 850 3ECHT(b) NAA 1675 20 Cool to 1000 F in 45 mlin. cool to room

temp. 8 hr at -100 F 900 24CRT 850 AL -- -- Cold iolled 850 --

SCCRT 850 AL .... Subzero cooled, cold rolled 850 --

(a) USS - United States Steel Corporation

NAA - North American Aviation. Inc.Armco - Armco Steel Corporation.AL - Allegheny Ludlum Steel Corporation

(b) BCHT - braze cycle heat treatment.

AS MECH~*ANICAL PC-.z C = T&E s~r-; CPR=Lq. STA11LESS STEL--S

CADCC 02 sarer-. - 2sý-44 ~tGf " IWOO pis DP= cc=

!7-7- 2H ussH TI jOSO 1-- 192± 2.7 L~~

uss T? in- 2.S LacL= aIuss =--i. 1 - a--,

ýIA Ti! 1075 Vi9 1772 1.0

A:T-1i c6-ý%) 1-9: 191 9.0 .2 cs

__i __ý 2--(c) --1 -_ *~t

ai Q$,YP) =70 Z79 C..2

P I l ý g ! 0 u s s ~ T : -2 :: C 6- i a -S

N AA __ 50 S..0

3CH7 10 ~ 4 7.0 !zda

;sl W.05i) =MCC) 216 6.5WC

Arm=, --id5) 1-5 j£ or-

-A-11 ass IAA SCs £59 2

A de) CýSS0 ss_ =42-S Lcze2ALM 5Cz- SW0 ;s; =e.. 'l

AL ~SCCVT =-: 33 5 -6

XIVA - !:='- A---ica= Ao!. c.

AL - AUIcspLtF ; =d ccl C=-.- .a&=-(i) kC t? !C .IS953. 2 SO =d 75~c =C=Of 7ield S=~g

(eCA)~g of two b==s.

A.....-- of t-0 c r z be lm

s4 it= 35£s8.C)Spccic=± ~!±: dcz& of Kg-ge muks.

Stress-Crro•ion Results for 17-7 PH

.Ml of the stress-corrosion data that have been reviewed for Alloy 17-

7 PH are tabulated in Table 7. Exposures at Kure Beach, in a 20 per cent

saft spr•.y, to a cyclic humidity cycle, and tu s-mfindustri.l envirorrnentsat scveral localities were evaluate'i. No failures were rerorted for ex-oosure

periods of 350 to 730 days at any of the three sernuiindustrial locations in-

cluded in the tests. T`-.e appiied stresses ranged from 63,000 psi to 243,uO0

psi. The environnmenti were described as mild to sern iindustriaL No fail-

ures were reoorted in- a few tests in the 20 per cent salt spray or in a cyclic-

hu..-n.dt- en--iror-r- nt. The applied stress levels in these tests varied iromn

63,000 psi to 126,000 psi.

Exvosure to a marine atmosp'_ere at Kure Beach, however, did cause

some specu-n.ns to crack.- T-he four allo-y treatments included in the tests

were TH 1--J55 TH 950, RH 950 a-nd CH 900. It is interesting t o note that the

CHi 900 soecixnens stressed to 143:000 and 214,60C p - did not fail in

74-6 da•ys 1 vo-sure co the ma•-ine atmosohere. These were the strongest

alloys tested but also the ;east ductile. The resistance of 17-7 PH wo stress-

corrosion crack-ing when in •h--- CH 900 condition is probably related to the

fact that transform-.ation of austenite to -- artensite is induced by cold work

rather than by a heat treatment. in the lzater case, precipitation of carbides

at grain bou•d•aries mnay- result in the develop=ent, of corrosion-susceptibie

.aths that favor stress-corrosion crack-ing.

Examination of the data ir the alloy shows how difficult it is to make

quantitative ev!-alations of susceptibility to stress-corrosion cracking. In

the TH 1050 con-dition, for e-_zi-mpie, 7 out of 27 specimens stressed to116,000 psi (75 per cent of the yield strength) Lracked in an average time of

2•days whereas the other 20 did not fail in 320 days' exposure at the 80-f-ot lot at Kure Beach. In a test at the 800-foot lot, Z out of 5 specirenas

stressed to 151,000 psi failed in an z-er.cgc "une of 100 days, while theunf-uiled =peci-i-s wer-e cxvoF f"or a total time of 746 days. No expla=a-

tion has been offered for the wide spread :n exposure periods betwe:n the

specimens that cracked and those that did not crack. In a seco-d heat of &-eArmco steel in the TH 1050 condition, but having a Inwer yield strength, no

"failures were reported for 746 days ;n, speci=.ens stressi.d to 134,000 psi-

!= the RH 950 condition most 0)f the specimens stressed at 90, 75, and50 per cent of the yield strength (183,000 to 102,000 psi) failed on exposureat Kure Beach. The exposure period to faliure ranged from 2 to 116 days,

deo-ending on the stress level and conditions of exposure. Here again, the

snecimens that did not fail w-ithstood exposures of 380 days at the 80-foot

a lot and 746 days at the 800-ft-ot 1--t. In the RH 950 coandition the .z.oy is

I

T.ABLE 7. RESU'LTS OFi ~L A~~ TESTS ONL ALLOT !T-? PH

AH~OY ~ Per Cc= to~ of Itzbacd

~~) 75 151 5 2 100 7;az5 134 0 --

A&ýc 5 10! 0 T=v-

117?P H ý) USS --1 ;3*. - --

US75 ls51 1-L-~~S 5~~ 14,1 - -5 -Lc±fa

1--7 FS. iR&i be t SS 9k2 !:3 - -

LS~S -S isz 321 z 53) i atEss so 1.0-1 -- -- 16t - L zji

- 75 1 Ca --

A~~4) 75 1435 Sr s S1.6AM---(c) so ~ 112 -s N1.2A-c=(C) W' 11.) 5 1 il. 75 rmr.~-

~ ,-.. - (C) a -25

M ~ c Tit, 1,43 -- : Z6 3

17-7P~.Th140 93A 3 -- 2

C~~c j =.;., - Fdjin~e 1h ce1 sk; 7.1- Cc~z

C lri - V.S f t

.- PH- T-H 1975 -YA 125:: 3 - IL~rsIAA ) 5 3 0 -- 51

42Z 93 3 -- 51

r-7 m. Trg uw uss(c) 'Z -A 9 -- 5)

3- 0 351-e-)

~77 H ~ 07 !AA7 ~ 5) 15 3 0 - 35'121eiz1)

M'AAW5 43 ED 3 3 - S. ~~17- S3!2~ sso S 75 :52 7 0 -

.A---w I)19s - 0 - 3

17-7- =-i CHi 9)3 A~c* so -a)- -73 o

Fo=== Cam cm tht IDUClk3od

N)j LISS - U.S. Szod Cccrxcat

NAA - A=cj= Arizimnc L-c.

A-, S:X-fooc 3om

(d) Avc=ýc 01L-e=o(C) JAZ==i--a.- at 3. oeiii3e. PC=,ylr=aL.

th) spod 'c c m i . LtAcc3 ' .j il

Z10

roin~whar stronger and 'less ducxt2: than in the TH 1050 condition, andconsequently it is z.iso mnore susceptible to stress- corro sion creacking. 11,should be noted that the data in Table 7 does not permit direct c-oraparisonof results in every case because of some spread in the mechanical proper-ties of different heats of the same alloy, =nd because some specimens werecut in the dirprtion of rolling and tAhers in the transverse direction. Aiso,the diiffe renc e in the severity oi the environment at the two Ktzre Da-_h lotsshould be considered ;... Coriq-1aring, the results reported-

A few tests were? made with sp-cirnens in the TH ;0 condition. Fail-ures occurred within a ftw days, 2!-enn on the specim'ens stressed to101, 000 psi (56 per cent of the yield strs-noth".

Summrarizing, 17-7 PH alloy in the highest strength conditions andhigh aD:)i'ed stresses was sh-own to be --usceptible to stress- corrosion

cracking in a marine atrnosphere. The suscepti--l~ity is not solely relatedto the 5trength of the alloy but is allso deter.mnned by the! heat-treatarientLprocedure used to obtai: tee properties. Sforne specxmens were repor-ted tohave beent cut u.aiallel *,r- the rolling direction and others transverse, but nodirect comparisons of the e=-fcct of this variable -were mnade.

Stress- Corrosion Resul:s for PH 15-7 Mo

!It was siatId earlier ;in the report that the cold--.aorking and heat-treating codtesfor PIH 15-7 Mo w~ere the Same as those for 17-7 PH-These are giv.;en in Table 5.. and the rriechauical pro etes of the het

tested in corrosion are in Table 6.. Table 8 is a tabulation of the accuimu-lztcc- data- on stress-c-urrosion cralcking for PH 15-7 Mo treated by thecommon procedures, and byv simulated brazing heat- :reazxnent cycles.. Spee-_mens ;;.ere eaiosed to serni.industriall atmno-qnhe--es a'. the SO- and 80foot lots .t zmure Beaclk, in a 2~0 per cent sait. srn-.2v, and- in _- cyli utziditvatm..sphere_ These were essentially -!.;_cates of the tests on 17-7 PH justdescribed. Ho~ever, sorne newer -ork by Armt-a ;i-n Nsor-jhA-.taE-on is :ncl:uded.

T he results shot' that the alloy in the TH 1050 is quite susceetible tostress-corrosion cracking in the en'.ironrnent of the 811-foot lot zt KureBeach. A large percentage of the specimens stressed to 60 and 745 per ce.ntof their yield strength were reported cracked after relatively short -xposurevericds. No failures occ-urred in 466 days on the speci...ens stressed to only40 per cent of the vield strength. Just as with 17-7 PH, however, there wasa wide snrez-3 in exposure titnes between those soecl.-meas that di-t 7aill

CcJ Ofn~ TToiem!aI

4

AcH 6) 4; 19

!25 71 46FTx~- 35 -- 466

A ~ 4 ~ s4 50 ;-:;

L- SS 1) IS - ~ - 12-

ESS Sri :01 - ~ 9 -

M3 5 =B.2 -

A6)ew 12 5 .3-

A~~7. 42 5 1 5 4

MO 3- .!o RH 1~kw A3,_o 6) 131 ! 40 6Aco m) 13 39 464 7r-cscic 40 S33 466 T~A ~413 S6 5 0 1- 466c

H .C) RION 142 5 5 -- mic) 140 4;.2 -=rc

A -..- 441 93 S 49.6 -

A c 4; 94 5 I.6 - ~ ~ c--

~ 75 164 S S 39.5 -- 7 Si'~scGOc 6 IV. 52 4(r.~ 61) 125 50 - 4;6 -

A:= W 2 !9 0ZZ-T .--

A4 = s 5 4 - .

AZZ4 -4 s 0 -ec7=cA:==o 43 32 50 -. S Tzzr~s

F.- 15-7- m~o. 5C-1 S52 A 75 1:; GA 6..S - u'~

A : x 1 3 1 5 4 61S - T r= m ~6) 1=1 5 4s 173 465

A--..* 6 131 s ± 4S6 i6-r

Aý ' 116 5 S 169.4 - =r--S

Az== 421 1 3Ns 4i66 !==c~scA-=w 4. 6 5 0 -4E6 .9 ~AZa, 4)S 466Tb ~ s

22

TABLE 8. (Continued)

Applied Stress Average Exposure TimeAiloy Source Per Cent Number Time to of Unfailedand of of Yield of Speclmens Failure, Specimens.

Condition Dar4(3) Strength 1000 PSI Exposed Failed days clays Direction

ExPed at Kure 3each. 1100-Fnor I nr (Continued)

PEI 15-7 Mo, RII 1050 Arunco '10 131 5 0 -- '66 TransverseAriuco 60 129 5 0 -- 460 TransverseArmco 43 88 5 0 -- 466 Transverse

PEI 15-7 Mo, BC|IT(c) Armco 60 140 6 5 23G.2 -- TransverseArmco 60 140 5 5 1,01.4 TransverseArmco 40 93 5 0 -- 466 TransverseArmco 10 94 6 3 333 466 Transverse

Pti I•-I Mo, Cif 900 Armco 75 196 5 0 -- 746 TransverseArmco 50 131 5 0 -- 746 Transverse

Fy~pve to Salt Spray - 20 Per Lent NaCI at 95 t 3 F

Pit 15-7 Mo, RH 950 NAA 80 178 2 0 -- 42 LongitudinalNAA 40 89 3 0 -- 42 Longitudinal

Pit 15-7 Mo BCiT(d) NAA 80 176 2 2 7 -- LongitudinalNAA 40 88 3 0 - 42 Longitudinal

Pit 15-7 Mo, brazed(e) NAA 40 - 0 21

I'll 15-7 Me. BCill"(f) NAA 40 0 21

Cyclic Ilumidity Exposure at Relative Humidity of 05 Per Cent or IfigherIlcat from 80-100 F to 160 F in 2 hoursHold at 160 F 6 hoursCoo! in 80-100 F in 16 hours.

Pit 15-1 M.. Ri! 95f.1 NAA 80 178 3 I -- 51 LongitudinalNAA 60 134 3 "" -1 LongitudinalNAA 40 89 3 0 -- 51 Longitudinal

pll 15-7 Mo, BCHIT(d) NAA 80 176 3 (g) 562 6 2(h) innsltidinalNAA 40 88 3 0 51 Longplozainal

Atmospheric Exposure

PI! 15-7 Mo, TIt 1050 Armco(i) 90 186 0 '730 Transverse

PH4 15-7 Mo. RIf 960 Armcd1) 90 198 0 .- 730 TransverseNAA(J) 80 178 3 0 3 50 (k) LongitudinalNAA(J) 60 134 3 0 "" 3 50 (k) LongitudinalNAA(J) 40 89 3 0 - 360(k) Longitudinal

Pit 15-7 Mo COf 000 Armco(i) 75 196 5 0 . "746 TransvesteArmco(i) 50 131 5 0 -- 746 Tranrvene

Plt 13-1 Mo. BCHT(d) NAA(J) 80 tic 3 i(S) 10O 350(k) LongitudinalNhA) 40 R8 "3 0 -- 350(k) Longitudinal

Pit 15-7 Mo brazed NAA(J) 40 -" - 0 9-o(k) Lt8gtudinai

Pit 15-7 Mo DCIIT() NAA(J) 40 - 0 2 90(k)

Footnotes appear on the following page.

23

Wz lEss - tlriz su'cs sz- Cc~c aA - A-=CD &Scc CAX=o=ca

(b; c~sc C4 t.ýcc 5,eceý cce.%C) S-e MeC HTi-%.c 5..(d) Set ---&A SCIIrr. Tj~e S..

1,25 F *==s ~wCC a1- (45 -=Im% 2= owo! to =.m :zc a=

3 b=

W)Sci~ pcr ITr -- --

(j) 'i Ce .o-c ý I(~ t !i

and those that did riot fail1. Ln the grcu-.ý I%- ;"clded failed svecirnuns,20 of 27 spec;.:.ns failed a&ter exposi'.c -periods of 16 to i82 days. Of the=±niancd soecimnuns, three were e-XpOsed for 2-10 days aund four for 4o6 days.The data in Table 6 show what etnerent 11eatt. treated to thee sam e strengthlevel, ar-d exp osed at equal stresses, show a wide variation in, average Zimesto faijure, 7! to lS2 davs in one in-sta.-ne. Evidentiv, ti-z induction period,during, Which corrosion and crack form-ation take place, varies cicnsiderablybetween ren~icate su-e :im-ns within a huat and also between similar heat---

At the 800-foot -ot at Kure Beacli, no failures were reported oic PH t1-5

7 Mo specim-ens exposed for a total of 4166 days. This included 15 s-oecL'-nen-s,-tressed at "40 per cent 0: the yield streng-th (applied stress about 125,000 asi).Dunhicates enudat the SO-foot lot had shown numerous crackidng failures,-vhzcn- 'Is a nmeasure of the difference Ln corrosiveness of the t~wo exwosureenvirmnments.. In an earlier test, 8 of it' specimens of PH 1-5-7 Mo, TH 1050stressed:-o 755 oper cent of th= Yield strength were cracked after exix-sure atLthe avi-foot lot.. Here again the average tirme- to failure ranged fro= 40 t!C3 days a-zt ihe unfaled speci-rens withstuud 746 deys" expoosure.

:': 15-? Mo i-n the RH 9509 condition appears to be quite susceptible tostress-corrosion cracking in the marine environment at the 80-foot lot atK-ure B3each-. Many of the speclimens in this condition failed during theCourse of the tests., at all stress levels. Average tinne t-- failure rangedfraz= 12 days for the most highly stressed group of speciniens to 173 daysat lower stresses- The m-ost resistant soeci-mens were those tested at*40 per cent of the vil tength (appie stress of about 87. 000 psi)- E-venunder these conditions, most of the specimens cracked-. O2 the other hand,-he group stressed at 50 per cent of the yield strength 1: !Ci, 000 psi) showedno failures during !75 days' exposure- Pt-rh.-s this is an i-ndication. of adirectional effect since the specimens in this erouD were taken in *.Ie di-rectio-, of rollin~g-

Some specimnens of PH 15-7 NM.o, RH 9150 failed at the 800-foot lot atKare Beach.. Ore speciunen stressed at 87,000 psi (4-0 Der cerat of yi-eldstrengt:-3 failed aftEer 34-6 days' exposure, whfile at higher strzss !cc.fail-uires oc=:-red in shorter periods- These results indicate that any excposure

Stis ahIov :-r. the ifl- (15 -cmiion to m~arine atrnospheres shouldi bpe at reia-±-evLaw stress el-

Stiecimcnzs in the R' I 950 condi-tion at stress levecls from 89,000 psi to178.000 Dosi were týlso exposed to -,x ) per cent salt-s-pray solution for42 days ared :,a the -,C-clzc buzniditxcviomn for 51 days without failure.AS discust.4d above, large perccrst~ag.!rs of simni1arly stressed . -,r-mens fz~iedin a sea-coast iron t.At sinmijar stress levels, Eailures -e- theSO-fbo: lot occur.ecc generz~y in slhorte- periods than the 427 and 51 daysUstecd for the sett-spr27,-.-d ha.iycyclez. This might indicate- that theK~ure Bezach envirovnmani is ma.re harmnful, lrat perFhaps other factors also

ova czarz in the results.

A few" tests were -.ade on PH 15-7 Mo in the RH 1050 condition. Speci-mens ;n this condition were more resistant than ia the RH 950 conditions atboth the 80- and 800-foot lots. At the latter site, none of the RH 1050 speci-mens f.iled in 46-6 days' exnosure. At the 80-foot lot, the RH 1050 conditicrshowed somewlht be.tter resistance than the Til 1050 con-dition. This mightbe expected on the basis that the RH 1050 szructure would have fewer carbidesprecipitated at the grain boundaries, and somewhat reduced tendency to inter-granular attack.

A few svecimens of P-H 15-7 Mo i. the CH 900 condition were exosedat Kure ~each. Very hig.h strength is deyeloped during cold rolling rather

Lan by heat treatment, so carbides are not precipitated at the grain bound-ar is. No failures occurred- -n e,>xosure for 746 days at stress levels ofi3!,000and 1 p6,OO0nsi.

The final test treatment was designated as BCHT, i- e., braze-cycleheat treatment. This is inten-ded to snimulate the co-nAitiors that utrvad dar-Ing brazng oi the alloy. The cycles used at Armco and• l'orth AmericanAviation are giv-en in Table 5. The auste.nte conditioning step at !625 or1675 F' will cause some carbide- t'•- recipitate2 probably more than at thestandard 1-750 F -cemoerature amd less tian at the 1400 F temperature used toform- the T co,.dition. .Additional carbide precipitaLion may occur during thecooling to 1000 F in 4-5 minutes. Howev-er subzero cooling is required i"each case to transform ::u-. stenite. and further strength is attained by

.-. i_.at. "hardei•i=. . According to Table 6, the Armico trea-Inent usingthe 1675 F conditioning step and a 24-hmur aging at 900 F, resulted _;- a some-what stronger, but less duct"le, condition than the North American treat-r.e.enlt in the latter, the conditionng e'mpierature was 1625 F. and the agingtreat.ne~nt =as cozrducted at 900 F for 8 hours.

A direct com-arison of the effect of these treatments on the suscepti-bility to stress corrosion was not possible, because the specimens were ex-nosed in diffcr--nt e=virc..nents. T-•enty spe-imensa of twent" with the .A-r--IcoBCHT treat-ment, at stress levels oi from 93,000 to 140,md-- pi, failed afterrelatively short exposure at the aO-foot lot at Kure Beach- A-t che 80'I-fonilot, 13 of 20 specimens failcd. Failures also occurred in the salt spray o'.the Nor-'h America- Aviazion BCHT s=eciz-ens i' the highly stressed condi-tion but not at lower stresses (88,0010 Di-. Here again thc tctal cxposuretime was only 42 days as Como-.red ýit 966 dayS on the pec .. en. exposedat Kure Beach. A comparison ith 0North Am-rzica- A-,riatil speciniens inthe RH 950 condition, exposed to the salt spravy indicates th=t the BCHTtreatment results in greater stress-corrosion-crac•.ng susceptibi'- ty, butthis conclusion is based only on very limited testing. Specimens :.,% theNorth A.-merican IRCHT condition were also ex-,posed to the cyclic hwnidityern.-ronment for 51 days. Ozze soeciw.•. crar-ked, b-t this was att. -ted toimproper cleaning fo=o-wi_ the heat treatmnenL

.Atnosphri-ic exposure at -Middletown. Ohio, for periods up to 2 years,has =ot resulted in any stress-corrosion crac-king failures on P.11 15-7 Mo in

26

te TH 1050. R1! 950 --r CH 900 conditions. Other tests in the L"s Ange-esatmosphere are still in progress, with no failures renorted.

Stress-Corrosion Results for AM 350and AM 355

Thm-se aloys are s.milar to 17-7 PH and PH 15-7 Mo, both in mecLan-icai ana thermal. treatmnents and in strength properties. A discussion of thephysical metallurgy of the alolvs a-.-r be fouwd in DMIC Report I 11 (-! md ina Dape by Lula(4 ).

The stress-corrosion-c rac-ingg properties of AM 355 in the CRT andSCCRT conditions were examined by -Alegh-eny-Ludlu.n Cor-joratior. Thedata tabulated in Table 9 were taken from a preliminary report issued in1959. A few. adin-tion-alldt on AM 3-50 and AM 355 L-n the SiCT condtion andalso treated by t-c braz. -cycle treatment (BCHT) from Nor-h AmericanAviation tests are included -.-. T-le 9-.

-' he c..-emical comipasition, heat treav.:ents -and mechanical propertiesof the alloys are giver iz Tables 4, 5. and 6, resnecEvelv. -it wi"i Be notedta strengths up to about 300.000 psi !ere develo=d by the SCCRT treat-ment on AM 355. Two different heats inf .AM 355. CRT ---ere treated to pro-duce markedly different properties. These should be noted bec"ase the re-s-uts of stress-corrosion cracking also -erc e"CRT 850" does o-t disting-u-ish the ttai=ce i- --'- o -eats.

in the Aleg-hew udnm tests, specunmens werc ztress - at 10, 35. SOand 70 per ce~t of tc ulti.muae te.nsile sireng~s. A t... T.zble 9, showsthat no failures occurrod in. any x-.posnre at She r lower stress leve!s. Azthe 80-fact lot at -- ure Beach, ..peci••ens from z!e h--,#er-st-.e:gt.h heat o!AM 355, CRT 850 (tensile streng-th 238.*-sill -:. fai-ed at both 50 a-n-07 percc---- of tixe tensile stren-guh, *whereas tho-se- frmhe iower strength h-at

{icnsilc stre-•.-g:h :0..g .) did nor ZI'-d Ln 321 davs' exposure at any stresslevel. At mhe 8S-0 foot-:ot, spw-ciwis 1f r- both beats .idwhen "-Sqcoto ?0 ,er ceat of--•t tensile streng.:-. :'•5 c.-na:on was gi-en to acco-t

for tLe fai!ure cf one s-o-ciren at *t- ¶3O-fo-o lot, n-eas duplicates at the=.ore severe S0-foot lot did not -ai.. ixno-.ure to salt srr-v als', resuted incracki-mg of sper-imens Lr--.-n the ",E "tr sztrcngf-h hea.- -ere-_s the lowerstreng-, specirmens did -ot fail. At the 70 Fpr cent s"ress level, one seci-men f-i!~i in one day. a.--i fts duplicat-- did t far1t : 3-"9 e-ays, It was noted&-a.t similar ex-e--er.ces at U- S. Ste-c were a-ribucd to pr-ibbihty effects.Secimens of both heats o' AM 355, CRT 850 stressed tr 70 c- ce-t thetensile strength -- d exptse± .z. the .-'ospre at Brackenridge -- * failedafter 1•1 and 321 days, resp'ct•rvely.

a -;- SCCRT 850 condition, -aiur-es oc-urred mr"ly at the 80-ft lot atKure Beach, on specimens st:.-ssed at 50 and 70 per cent o "hei:r tt-.-silestrength. Since the alloy iin this cc.'-ition is very stroang, tlh- zpimied sztcss

I-lliii i !i i

27

TAI :.1SP-ILTS CE S-12SS-cOX0N-cPACKM I EOY IAUAOYS AM! 350 A1MD AS-1 M6.

A-- Cc= c EXNZ= T.==

3&,-A aC3 .1C- AL !D 23-8 2 o -

JL35 Z- 2

AL L* !1941 ± 2 CIS -- 1~~

AL !-0- i=- __

.A 3' S. :--. -=dc miza

AL so 14 2 *.-

-W --t~ sc=r:Z L

a:35 ME- 4,

ILL 50 !52..C 2 3= 319r5

AL -40---A0=

A= =.* SrC-- iv .

AL35 ;C-.---

.4± ,e Z-2. SIZ 0=- -- 32! P=C=Mc!.--;-= 9,

AL 3i S3..4 ft 35 i^- 3±1Z2

AL so 119.2! t 2 I-- 3± L 2

ALL TO I4. S& _2I 3:1 _J

-w35 a -- ) AL-35 -12-4 2 --. 32 _____

AL so ~ 1. 2- 3411L4

AL TO~ S lT-. cC ;s c S

S3ts. Z50 At- i0 3*.s 2s 0 -- 339-

AL 3±13.4C, 3±5.

AL so 01. 7 o~

AL IV =48. 2 113n9

AL± 10 =11-3. I= tL -- 344 L -3

.4±-' 2 - 0 - 24

At± 23 1C.. 1 0 - 31 T=

AL 70 -10.3 2 1 12 1.

?c azc=! Of~ T==

- - -.. -. ~ o sr--c Sp -

Aml 36-5 9-- AZ7 . 3 3 ---

zl I ..t -;;,4 r NAA 3-ý .x -

:NAA 4r- i LX 1.C - ~~

.~ ~.~.I~ AA3 3 3.5-

-AZ4 Sa--a 3 ~

CL C= N-i Sk

A.3 353. sct1.z :--c, ,.L :;0 3%4--3

AL.0 s.-cl - X-

AL 13re-

:1353. Cý-T AL .:Q --

M335 SCC~r S d) Al.. C-

nu Se US 3 .3 INC-

-5c 3 =4

-;Co -;

:L. 35. qm.c MU3.3 t 3 - -.

ICAAs -;C _ 3 1 Us ()

,;;E 3,z. SC7? --:sdc 3LAL Ze 14Z 3 3 Ila1 .

N-- = a 3 a3 =3 1-5--

AS!A 350. T 3 3~ 4-

ZZA 40 63 3 3 !51 -

29

TABLE 9. (Continued)

Appl cd StressPer Cent of Exposure Time

Alloy Source Ultimate Number of Average Time of Unf~iledand of Tansile or Specimens to Failure. Specimens.

Condition Pata(4) Yield* Strength 1000 PSI Exposed Failed days days Direction

Cyclic Humlility Exposure at Relative Humidity 95 Per Cent or HigherHeat from 80-100 F to 160 P ui 2 hoursHold at 160 F 6 hours

Cool to 80-100 F in 16 hours

AM 355, SCT 850 NAA s0* 150 3 3 12 -- Longitudinal

NAA 600 113 3 1 13 2(gh) Longitudinal

NAA 40V 75 3 2 26(g) 51 Longitudinal

AM 355, OCtIT NAA 80' 1510 3 0 5 ,2(h) -- Longitudinal

NAA 400 6 6 3 0 5 2(h) -- Longitudinal

ANI 350, SCT 850 NAA 80' 140 3 3 12 -- LongitudinalNAA 60' * 05 3 3 13.5 -- Longitudinal

NAA 40' 10 3 1(9) 14 51 Longitudinal

AM 350, lCHT N.AA 80' 136 3 3,, .. Loftgitudiaal

NAA 40J 68 3 0 - 5 2(h) Longitudinal

Indicatcms percentage of tensile yield strength.(a) AL - Allegheny ,i:dlum Steel Corporation

NAA - North Amerinan Aviatic~n, Inc.(h) Heat 35526.(c) ileat 35806.

(d) Atmospheric expsure at Brackerridge, Pennsylvania.(e) Atmospheric exposure at Los Angek.s, California.(f) Test still in progress.(g) Specimens not properly descaled after heat treatment.

(h) Spcchmens partially fractured.

30

was oer- 200.000 psi on some spec-imens. No failures occurred at the

S30-fcut lot or L! i 20 =rr cent salt spray. These specinens were all cu!longitudin•diy: i.. e-, in the dL-rection of rolling. A strong 4di;rectional effectwas rcvealed in the salt spray. Specimens that were cut transverse to the

direction of rolling cracked .ery quuickly, even at an applied stress of a-cut:)s:. T?, c--ect was z-.so -,bserved in the atxtospheric ex-posure test.

AI 355 in t•e SCT 850 condition -was evaluated in the Ncrth Americzntests. In ilii. cundi-io=, the aI.oy had :- -Icld st; z-ngtb of about 190,000 psi.The data in Table 9 sh)w th" the alloyin this condition is strongly st.s:euti-

e s ai. Fai-lures occurred in all three environ-ble to stress-corrosion crc a•..ng •- o

.- ents, even at thc lower stress lcvcls of 4-0 per cent o- the yield strength(75,000 Ds,). This is probably reltid o carbide precipitation during Tne

L-anneal, which con.di---is the -stc•nc't zo•that complete transformrtionII- o'cur during subzro cooling. Carbides are precipitate- at the grainboundaries, -whrch prest-u-abiy results in corrosion-susceptible paths. Aco-nar-son of :ae results of a _sn. er.c ex=osurc tests for the CR7 850anId :he SCT conditions at comuaralb. c stress levels shows &-at specimens inthe SZT condition are susceptible to cracking, _hereas those in t-- CRT 859coztinon were ozi E~ox-msures were a: different loatkozns, hut it is probabic"that transfeorration by cold rolling (CRT_ occurred without .&.e precipitationol carobies at the -rain bouzdaries (as in the SCT condition): an--"- thereforeresulted in a structure less sascentible to stress-corrosio. cracking.

The braze-cvcle heat trzatment BC!TI) -hi;ch includes the slow co-.lingfrom 1675 F to ICOG F, resulted in slightly lower properties (yield strength166 .000 psi). The alloy i". this condition was also susceptible to cracking.Based on the renorted data. the times to failure were slightly longer than forthe ajo-.- ite SCT 850 cordition. "o-,.'-ewer t-Ze were of the same o.-erof ma-.itude, and the differences may no- be significant.

The North Amnerican Aviation _ro-ra•-- so ".-.-r--" 3,.,SCT 850 and A•Lt. 350, _ C-HT. The• results -were similar te th-ose - iAMN, 355, and t•he same co.-m--ents appply.

Martensitc and Ma-tensitic Preci-itation-Hardenable Stainless Steels

In these two classes of steels, the anstenitic structmr• is transformedto martensite during cooling to roorn temperature from the annealing tern-peravure. High strexng-S is devreloped by subsequent tempering oiLprecitDUsion-hardening trea-ments. Three steels, one martens--ic- 17 MoV,and -two tartensitic precip itation hardeanable, Stainless W and 17-4 PH - !%vebeen tested for susceptibility to stress-corrosion crac.ing. T che.-r-icalc.mrosiiions of the steels tested -re given tn Table 10, and the det-als of th=heat treatments and mechanical .rouleriics are in Table I-I

31

TA1:Ez 10. ClEMAKAL COMPMMS O~na S&hE3ARMDSMfC AND S6#AMca trliC_

Alloj DjLt-A) C P~ S SI C: K10~ V i; N~ A; CS Cb

MS. S ;%5 z C-4 O O~j *-%05 t.-4S V. !O 0iZ 0.9.5 u.~-- -3--

W Uis U. I, _ e. . 0 *14 v.u]3 ;,:- :1 f C.66 0.?1 - - Sf- 0.034 0ý& -

.:-~;~i A~w (I_22 0O2 0.01; 0.41 1.7 1~. - --'s 37 .2

17 -44iP Arcc O0.03 0.±.X 0.CW 0.0H a 0-C 1&S1 *SM- -- 3.4c0 G

4Ai M~S-~l S_ S---!c

-, c Sc.1_ýo

Sir-tss-corrosion data for the 12 Mc-V- and Stainless Ix grades wereta-ken Iromn the U- S. Steel renortt3). and those for 17-'s PH sheet are :)re-

~nrv iata from- incornilete tests b--in- -onducted b~Azc. h euta re tabuft-ted in Table 1I..

T-%e- data i:n T able I I show that the heat treatmnent selected for 12 MoVallloy resulted i-n high strength. The yield strength was over 205,000 psi,anid corrosion tests at Kure Beach (80-foot lot) were carried out at 50 and73 Der cent of the yield strength. 12 MoV alloy, in the condition tested, isstrongly susceptible to stress-corrosion cracking. This was also the coni-cius: -on from atniospher-ic-exposu.-e tes'.s at M rvieWhere 45 of45 specimzens (at, 75- er cen-t of the yield str~ngth) failed after an avorageexncnsure Deriod of 5 davs.. Additional work- has s~hownz that the allov was not

susentblec. tres-crr~~oncra~czg wen tempered at 1 100 or 1200 F.Under these cond-itions, )-iev~er, the L-ield strength -mas rep~orted to be

33~,Zx6 psi, ccoosiderab!- !olrcr uhan that WO~ie b

Szainiess W, was also; hardened to a yield-strength level of abt--ZGO,GGO psi-. The hardening mnechanism in this case was by precipitatic-n ofcooun--ds of titanium and aluffminum within the naartens-itic structure duringthe aging treatment-. Exposure at Kure Beac h at 50 to 90 Der cent of thei-ield stren_=th- resnalted in. failmres wihn'l- z~iz:t-. . Duringoutdoor exposure at Monroeville, however,* no failure occurred over a periodof 520 days. Tlhus, at high strength levels, Stainiless W aD~ears to be samie-

wot Ore re -Sitnt than- 2' Mov.

The da;ta shown. for allov 127-4 PH are fror i-Oz- mazsarial in thia sheetform which has not been available heretofore. Specimens were cut from0. 050-inch sheet- The high strength in this allov is developed diuring the ag-ing step, which- causes precipitation of compounds within the martnsite-~

Agng at W00 F resulted in tensile strengths of slightly over 200,000 psi with

32

TABLE 11. HEAT TREATMENT AND MECHANICAL PROPERTIES OF THE MARTENSITIC AND MARTENSITICPRECIPITATION -HARDENABLE STAINLESS STEELS

Heat TreatmentAustrnitize

or

Source Solution Treat Tempered or Aged Yield Tensile Elospgation

of Temperature, Time. Temperature, Time. Strength. Strength, in 2 Inches.

Alloy Data(a) F minutes F hours 1000 psi 1000 psi per cent

12 MoV uSS 1,850 13 900 4 205 256 10.5

Stainless W USS 1900 15 1000 0.5 201 202 7.2

17"-4 PH Arirco 1100 10 900 1 181.0 202.2 9Arrnco 1900 10 1025 1 155.4 166.8 10Armco 1900 10 1075 ! 150.8 162.2 9Armco 1900 10 1150 1 113.2 139.4 14

17-4 PH. Armc:o 1900 10 900 I i83.0 203.5 4

solution treat, Armro 1900 10 1025 1 160.8 175.9 6

weld. and age Armco 1o00 10 1075 1 160.0 161.2 6.5

A rmco 1900 10 11.50 1 115.4 115.4 12

17-4 PH. weld, Armco 1900 1li 900 1 182.6 206.1 6.5solution treat, Arrnco 1900 10 1025 1 159.6 166.3 6

and age Armco 1900 10 1075 1 15:3.8 161.1 7

Armco 1900 10 1150 1 130.4 147.0 7.

(a) USS - U. S. Steel CorporationArmco - Anrmcn Sterl Corporatioi.

33

TAtZ M2 REZV!LTS OF IT~ r TST 0\ -a rZ'A~~n

AX L.. ZiS1T1C F?.EJ74PTAiG fA- .D£23-rJL STAL%1S35 SIMES

Erpos~c Tiz~e

AN f PC CC= di S~zijg= xo Fa i L--. cICmamcm D=W sa ~oco Psi days days

11 ldov Uss is 153.6 -.0 40 1 -

ISSS 50 102.5 - - -- 1_4b

uss so MSC.9 -- -- -0) --

Uss 15 230.8 ii 12 .4 -

17 - PHi. H 9-V Sr-o 90 ie-7.9 5 0 - 2A:=co 13c'.. s 0 - 2

17-4 Ph~. -:i0Q A.~xo :=-7 5 a-:-A--c, -.5 113.1 5 a -

17; F=. H :10 A~C 0 0 - 2

A---cO. 4. 5 0 3=

1--;F-..H I00 Ar~c s0 -- 3 560

Wr4ed. Thci- Z c~d A~

i7-. al. H10 -4o 0 u&;..3 6 -S --

T :I M.0 -

17i~1 ~2 A:=o ?0 143..6 5 0 -

A:=c 7s 119.7 5 0 2t:

-0- -.- C 5:0 - 322A.-zeo 7.S154 32

f:-li. H 23 A.-co S-- ai.. Q 0 -

A.---=a is 97 8 --

S2 T.-azcd. ofedcd, xi Art-ed

t--. . A=O 90 Sez- s 5 28-

A-*75 137.3 s s 3i --

17-4 FA. H 05 A.-jo 90 144.1 0 -- 32As='eo 75 22. 45 0 3=

A7-4 e 3. 6 0 3-

A=300 7S 1;215 5 0 - 22

34

TABLE 12. (Cositinued)

Exposure TimeAlloy Source Applied Stress Number of Average Time of Unfailed

and of Per Cent of Specimens to Failure. Spec inens,

Condition Data(a) Yield Strength 100C PSI Expsed Failed days ýdyb

itjLsed at Kure Peach. bO-Foot Lot (Continued)

Solution ieated, Welded, And Aged( ("antinued)

17-4 PH. H 1150 Armco 90 103.9 5 0 -- 322Armco 75,. !%. a 0 "" 322

Atmospheric Exposure(c)

12 MoV USS 75 153.8 4.5 45 5 --

Stainless W USS 75 150.8 7 0 -- 520

(a) USS - U. S. Steel CorporationArmIo - Armco Steel Corporation.

(b) Average of three specimens, or more.(c) Atmospheric exposure at Monroeville. Pennsylvania.

Data on 17-4 P11 ar" pre!iminary results from incompleted tcsts.

35

a yield strength of about 180,000 psi. Other aging treatments at higher term-peratures, i,.p to 1150 F, resulted in correspondingly iw.ver strengths.Stres s-c-rrosion-cracking tests at Kure Beach (80-fout lot) are being madeon both ordinary cpecirnens and welded specimens at 90 and 7i per cent o:'the yield strength. The composition of the weld wire was the same as thato( the test material (-.tee Tabl•e 10). After welding, one set of specimens wassolution treated before aging, to reduce or eliminate nonuniform strains orprecipitation in the adjacent metal. It would be expected that this should re-sult in a more uniform response to the subsequent aging treatment. Theother grnup was soluti.,n treated, welded, and aged. Heat-treating s'cale wasremoved by grinding oi- wet blasting with alumina grit and Pangbornite.After exposure for 322 days, no failures had occurred in the unwelded speci-mens at any stress level. In an earlier test, three out of fE.ve specimenscracked in 322 days, when stressed at 90 per cent of the yield strength. Theother two, and a group sLressed at 75 per cent of the yield strength did notfail in 560 days. The welded specimens in the I 900 condition, and not solu-tion treated after welding, failed within a relatively short time. This is anindication that welding is responsible for some change in structure or straincondition, as mentioned above. Solution treatment after welding was bene-ficial, but it did not prevent failure of the H 900 specimens after a some-what longer period of exposure. No failures have occurred in the weldedspecimens aged at 1025, 1075, and 1150 F.

On the basis of these incomplete tests, 17-4 PH sheet material showsgood resistance to stress-corrosion cracking in a marine atmosphere.Welding of the alloy in the highest strength condition (H 900) reduced theresistance to cracking. The standard solution heat treatment, followingwelding, apparently does not completely restore the resistance to stress-corrosion cracking of material. Therefore, in stress-corrosion environ-ments it would appear to be safer to use material aged at higher tempera-tures, if the lower strength achieved under these conditionb is acceptable.

DISCUSSION OF RESULTS

Most of the comments about the results have already been made in thediscussion of each class of alloys. From a general standpoint, it is appar-ent that the need for stress-corrosion-cracking data for the high strengthstainless steels has been recognized, and experimental work has been startedto providn quch inform--tion. A rcliablt evdluation of the susceptibility tostress-corrosion-cracking of a material involves the consideratic.nn of manyvariables, and consequently a large amount of time-consuming exrcrimentalwork. Therefore, it has been cmphasized that most of the experimentalprograms to evaluate the susceptibility of the high strength stainless steels

to stress-corrosion cracking are still in progress, and that the data reportedhere should be considered preliminary in nature. Furthermore, correlationof these experimental results with actual service performance has not been

36

estabi:shed as let. [tie fact that crackt!,g has occurred under some experi-mental condit::-s does t.ot mean ihat the alloy will crack under a-1 servi-ceq

con.-itnns. It is an indicatxon, 1'owever, that such an alloy s•.ould be usedwith due regArd to envirox-nental a sd tress condiions that =_vy exist in theintunded qervace.

Tabu!ations of the results of tests, such a . -it zchluded in ts re-Durt, Ioelp to s ia gencral way whaei has been done, -_nd to point ont-J.-re additional work -nay he required.

Txie results of tests reported to date are given ia Tables 3, 7, 8, 9,and 12. These show that the majozirv of the s-ecimen- were expo--ed to themarine atmosphere at Kure Beach. Laboratory test' .cluded the salt spray,a!.'ernate ix-•xnersion i• a •a--t- soiution, and a cyclic n.,.nidit- exoos,.re. Ex-D.su: a tests in seminous~rial outdoor a•r -.ospheres -,ere made at the loca-tions of the coxoDanie- conduc'ing the tests.

Anv nunber of compax isons of the datz could pr-:,bably he made, butat uhis stase some of the tests are incomplete. an.- inn other cases- th•re .S

idn.: enough inforination available to accnt'unt for the w-de so;ead oserved in

linies to failure.

it is tch be ex__cczed that the rnetallurgicat- str-cture deveioped by!hermnal treatmce-T, or -ncchz.ni.ai def-crmatio-i will affect the results. "heCi ý00 condt-ion for ex_.-rnp!e, resulted in the highest strengt:" but ti.ealloy was irmmune from stress- :orrosion crac.ing.. This may be rela:ed tothe fact !ha't cond:-._on CH 900 dc-es not in-volve heat treatr..ent in the tempera-ture range at which carbides w;i I precipitatc. Therefore, carbides at thegrain bowndaries -Aroulld not be (xpoected Ln alloy.-i--z the CH 900 condition.

Thie results for PH 15-7 Mo are somecwhat more censistent than thosefor 1P-7 PH_ e . gain, the allo% Ln the CH 900 condition was not sus-c=:-ible to cr_.:.;.kg in the marine exposure. ln this alloy also, the PH 950conditicn seenns to pr'•__uce a :.rc -- su_-u:=Libc.tr-cture than T.i..._Cracking occurre-d on tb-e RH 950 specimnens, at applied stresses as !,o- -.!87,06, psi, representing only 40 .er cc-it of the yield streneth. At similarstresses, th. ~e T ) 1s50 c.zndi&io. did noot crac.k by strczs corrosion- it wouldappear from these results that the- extent of stress-corroson cracking is notdeter•-•cd solely by the r--_ =e of carbides a! the gran bound--a-es, Such

.zctors as the q-antiy. ,- ',---ip--a-, , of di- rs=on. the st ture, ad itscomposition may be the controlling ccnsiderations.

it r-.uld be of interest to study the effect of these factors, a: well asother -microstructural details, such as the amou.t of retained a czrite, thepresence of deilta _-", -D perhaps the carbaon conte-nt of :he ma•tens-ite,a-- the stress-corrosiou-cracking prt•peerties of these steels. Of course,-=-tr varables Vtha a "ect results, that is, specimen -•-earatien, stessing,and det-ais of e_.posure, would have to be controlled wzd taken into accountin such a-- Lnestigation-

37

WORK IN PROGRESS

The resu|ks of the stress-corrosion-cracking tests on the high-strengthstainless steels that have been assembled in this report, represent a goodstart in the direc.ion of providing such information for design and materiaizieuIgILeers in the aircraft and missile industries. Some useful data have beenaccurnulaLecd. However, somc unexplained lack of reproducibility was alsoev.dent in several of the tests. While some spread in corrosion test resultsis expected, enough daa must be accumulated to attach proper significanceto it. Therefore, some phases of the programs discuissd in this report arebeing continued. Also, several new programs are in their early stages.

It has often been emphasized that maiay factors may influence stress-corrosion-cracking results. Work is in progress to standardize evcry phaseof the tests required to evaluate semiaustenitic precipitation-hardenablestainless steels. A report has beeu prepared(S) in which every detail ofspecimen preparation, heat treatment, stressing, exposure to laboratory-type environments, operating conditions, and reporting of results has beenspecified. A continuation of this work describes the details of rinw-tvpespecimenq for testin, specLmens in thc short transverse direction.( 6) Thework so far in both of the prograin., mentioned has been concerned with theestablishment of standard procedures. Testing will be conducted by -numer-ous participating aircraft companies and by Allegheny Ludlum and ArmcoSteel Corporations. Salt-spray and alternate-immersion exposure tests areplanned for stressed, strip specimens of 17-7 PH, 17-4 PH, PH 15-7 Mo,AM 350, and AM 355. Ring-type specimens for some of these alloys areincluded. Also, some specimens of AM 355 and 17-4 PH will be exposed toa marine atmosphere. This is a comprehensive program that should producea large quantity of valuable dat:t..

The difficultics of translating results cf accelerated stress-corrosicn-cracking testb into expected service rcsultn have also been mentioned before.A comprehensive program, sponsored by Frankford Arsenal, has been inprogress for about I year at Mellon Institute, Pittsburgh, Pennsylv,.nia, -Aidat Aerojet-General Corporation, Azusa, California. High-strength materi-als, including AM 355 and PEI 15-7 Mo, v hich are of interest in this report,will be tested for susceptibility to -st•iess-corrosion cracking in many envi-ronmeiits. The Acrojet-General tests will be in enviro,,tments that the alloysencounter during fabrication and storage of missiles. The Mellon Institutetests on the same heats of the alloys, will be made in synthetic and artificialenvironments. The work on these two programs so far has beer concernedwith procurement of materials, checking of heat-treatment proccdurcs,determination of the mcchl.nical properties of the alloys, preparat'.n of ex-posure facilities, and evaluation and development of the stressing procedures.Preliminary stress-corrosion tests have been made to check out the vnrioussteps. Artual testing of the selected alloys will probably be conducted withii.the next 12 months and bo,tild result in valuable comparisons of the effect ofmany synthetic and natural environments on stress-corrosion cracking.

33

A~oi~.r c~crht~sest ress-corrositw acking program is beillgtqond-actcd 1.1 thc National Bu*.reau c-f S3*ancia±-ds fcr the Rlu-,ati of NJezva

Wazons T c.itonh:J-=al.r stakir.ess5 steels in several heat-treatee' cor~dit:.ns arc includcd in. the list of alloys i.,eing evaluated. sentbw-am spcis-ns stressed at 5C.t, i 6, a n d (i per f'n ~ h il;~z-cngzh wtercexposCD3SI ine arine atmo~sp-here at Kure Beach _Ez

iii :ths a-Cl.

Addj.~~:eI~or ras --]so been d->nc or. -AM 355 anid AM 350. but it ---s

no', b~c-i repoorte6 yet- Thes'- data, ain=n& tx-th the results oi the other :,.ro-grant-s nco= i:t pr-agre-ss. shtould be ci great v-alue in the uiiacnof Migh-strength stainless steels a-, the hihstress levels desired in itiocern aircraft

REFERENCES

!~1 !~ *C_ J_. , and Boyd, W_ Y,.. "Envi ronmelna! aad Metallurgical£act~-7c -%f Stress Corrosi-.n Crarkfr; :-- Hiel- Strength Steels". D&UC

Renpor' 151 (A-pril 14, 196!)-

~ i Di, ~ C_ . and' Hall , __ 7-e Physical Metallurgy of Pre-cizaon-ard-.z~3-tainless Stceeis", DMIC Report 11I1 (April ZO.

(3) Phelps. E. Iiand Loginow, -A-.IV.. V.. S. Steel Corpxoration. -Stress

(1960).

()Lula, R_ A. Allegheny Ludlrna Stct-l "~AIM 350 an-d AM 355Pruzenr6es and TH-at T.-reatm er.t*-. -Meta; Progrns5, 75 (3), 1 :6 (1959)-

(5) ATCG Report No. -ARTC-21, Aerospace Industries Assocization C' rune- icla,iuc. , `Tv.ct Procedure for availation of Stress Corrosion Lna Preczirda-

tH arcentn-w Se.miattstcn-i-6c Stainless Steels", recprt to INtZ-nal Acaca-em; ofiSciences (October 15, 1959).

(6) loser. W_ R_., anid Deveam=, G D_.. '"ARlT C P-roject iE-39. ~rfcicot Stress Corrzsio= Teztiri for Evaicaticri of Stress Corrosi-'i of PN

Sem-iags-menitic Steels", Test A. Zvý-ahatiori of Machiaing, Akssembly, amndCalibrating Methods for A-RTC-Z2 Ring Speclirnexas, Report No- NO-R-61-3-S, e- ±e Cornporatiomr, Nlorair Diso (March 10. 196 1%

C.TS Ipa,

LIST or DMIC TECHNICAL REP~kTS !SStfW'DEFENSE METALIS INFORMATION CENTERT

Battelle Memorial Institute

Columbus 1. Ohio

Copies of thr. technical reports listcri brclow may be obtained from DMIC at no cost by Government. aZenc~es. and byGoverniiic~it contractor s. zubLontractors, and their suppliers. Otheri may obtain c~opies fromn the Office of Technical Services.Depa~tcmnt of Comnmerce, Washiiigingicn 25. V. C. See PO numbers and prices in parentheses.

n?..lCF(~ort iNuiber Titicle_____

46D DCpariinent of Defenise TitaiiL... ýh=~-Rolbssg Program - Uniforin Testing Procedure for Slicet Maersiabk.S~ptieiiber 1L2. 1958 (PB 121ý49 $1.23)

46F Department of Defense Titanium Sheet-Roliing Program - Thermal Stability of thL- Titaniumi Shcet-llolllng-%ý~u Aiiuys. Novit rr.her 26. 1958(PB 161061 $1.25)

-IfF eiucu f Defense 'ritaniurn Sheet -Xilling Program Statub §,,-Nit No. 4. March 20. 1969 (PB 151066 82.25)4rV: Deparsrneat of Defense ritinium Sheet-Rolling Program - Tim -Ttinp.-rature-Trainformation Diajrams of

the T~tanium Sheet-Roiling Progrinn Alloys. October 19, lAFC j.1' &5*- 75 $2.28)4611 L'epartment of Deferiu.; Sheet-Roiling Program. Stattus Report No. 6, June 1. 1960 (P9 181067 $2.00))461 Stastistical Anialysis of Tenisile Propeitles of Hecat-Treated Ti-4Al-3Mo-IV Sh~eet. September 16. 10160

(PB 161095 S1. 25)iu6 Beryllium for Sitrszt-iral Applications, August 18, 1958 (PB 121648 $3. 00)107 Tensile Properties of Titan~ums Alloyt At Low Temperature. January 15, 1959 (P9 151062 $1.25)

it,6 Welding and Brazing of Mnivhdenum. March 1, 1959 (P0 151063 $1.26)_9 Coatings for ProtectsnE Molybdenum Fro .i Oxidation at Elevated Tt-ipcramuc. March 6, 1959 (PB 161064

51.25)1to The All-Beta Titanium Alloy (Ti-13V-1'.Cr-5Al). April 17. 1959(PO 161066 $3.00)III The Physical Metalltugy of PreLirstation-Hardenable Stainless Steels, April 20, 1959(PB 1510W7 $2.00)112 Phmysical and Me.:hanic,%l Properi~es of Nine Commercial Precipitation-Hardenable Stairiss Steels,

May 1. 1969 (PB 1510168 53. 25.1113 Properties of Certain Cod-Rolled Austenlitie Stainless Sheet Steels. May 15. 1959 (Pe 151089 31. 76)114 Duc:,le-Pritt~e Transition in the Refractory Metals, June 28, 1959(PB 161070 $2.01))115 The Fabrication of Tungsten, August 14. 1959 (PB 151071 S1. 75)114R Design Information on 6Cr-Mo-V Alloy Steels (H-1l and X~r-Mlj V Aircraft Steel) for Aircraft and ldissllea

(Revised), September 30, 1960 PB 151072-R 81.26)11" Titanium Alloys for High -Temperature Use Strengthened by Fibers or Dispersed Particles, August 3). 1959

(PS 161073 52.00)118 Welding of fligh-Strcrigzls Steels for Aircraft and Mitotic Applications. October 12, 1959(PP 151074 $2.25)119 Hleat Treatment of High-Strength Steels for Aircraft Appllicatloiiu. N'ovouilwr 27. 19b91 (PS 151076 $2.60)120 A Review of Certain F..ir:n Castings Applications in Aircraft and Missiles. December 18, 1959 (tS 141077

:1. ýý)121 Methosd. for C'snductlng Short-Time Tensile. Lt..p. and Cr..ep-ltupture Tests Under Conditions of Rapld

Ht!Atlng. Vrceniber 20, 1969 (PB 1510?8 51. 25)122 riot Welding of Titanlwcr And Titanium Alloys. December 31, 1959 (PO 14"1079 51. 76)123 OMsdation delta- tor and Protective rriaringot forr fColumbium and Columbium-Bave Alloys, Janiiasy 10'. 1660

(PB 151080 $2.25)124 Current Tests foi Etvaluasrqiv Fratrnure- Toughness of Sheet Metals oo: High Streng'k Levels, January 28, 1960

(P11 151081 82. 00)126 Phaysical and Mecharical Properties of Columbium and Colurmbiur-!-?me A!loyg. Ftbruary 2, :960

(PB 151082 31.75)126 Stru:tujral Dama3o: in Thetmally Cycled Rene 41 and Astroloy Sheet Materials, February 29, 1960

(lbS 1010U3 so.'16)127 Physical ind Mechanical Properties of Tungsten and Tung~tet -Dlatao Alloys. March 13, 1980128 A Summary of Compakrativel rropcrle:. c! Air-Melted and Vacuuim-Melted Ste~l% and Stilwtmailoyii,

March 28, 1960 (PB 1510888$2. 78)110 Physical Properties of Some Nickel -Rlate Allroys. Ma 0o, 19~00(PS 151086 32.78)

130 Selected Short-Time Tensile ai~d Creep Data Obtained Under.Condiltosss of Rapid Heating. ui. Y?,)60(II :.loss 42.u2)

131 New Developments in the Welding of Metals, June 24, 1960 (PB 181089 $1.28)132 Desigii Information on Nicklel-base Alloys for Aircraft and Missiles. oitly 20. 19610(P8 151090 53.00)133 Tantalumn and Tantalum Alloys, July 26, 1)60 (P8 151091)35.00)134 Strain Aging of Refractory Metals, August 12, 1960 (P8 151092 51. 78)135 Design Information oin Pit 15-7 Mto Stainle~s Steel for Aircraft and Missiles, Auguist 22, 1060 (PB 1610113 S1.28)

i'i'.liC

s.epor• Numrher Title

115A The Effects of Allinying Elcrmen•s in T!taniurn, Volume A. Constitution, September lb. 1900 (PS 15109433. 50)

130 Tie Effccu of Alloying Elements in Titanium. Volume E. Phy-Jcai an.l Chemical Properties, Deformationand 'franssornaiuon Characterisrics, May 29. 1061

131 Design Information on 17-'o PH Stainleu Steels for Aircraft and Miusiles. September 23, 1960 (P8 151096$1.00)

0ý Availability and Mechanical Properties of 1gh-tetrngthSteeI ExtUrsions. October 26, 1960 (PI 16109', $1.75)139 Meltink and Calling of the Aefiactory Metali Molybdenum. Columblum. Tantalum, and Tungsten.

November 18. 1960 (PB 151098 $1.00)140 Physical and Mechanical Properties of Conmercial Molybdenum-Bate Alloys, November 30, 160

(PR .509911 $3.00)141 Titanium-Alloy Forgings, Dccernber 19. 1960 (PB 151100 $2.25)142 Environment.l Factors Influencing Metals Applicatinns in Space Vehicles. December 27. 1960 (PB 151101

$1.25)143 Mgh-St:enth-Steel Fnrgirg. January 5, 1461 (PB 1,•1102 $1.75)lA4 Strest-C..rorion Cracldng - A Nonte.hni'tal Introduction to the Problem, !anuary C., 1961 (Pb 151103 80.75)

146 Design Informnation on Titanium Alloys foe Aircraft and Missiles., January 10, 1961146 Manual for Beryllium Prospectors, January 16, 1961 (P1 161105 $1.O00)141 Th'ý Factos Influencing the H-racture Characteristics of High-Strenoth Steel, February 6. 1961 (PD IMI 1C0R

$1.25)14e Review of Current Datm on the Tensile Properties of Metals at Very Low Temperatures. February 14. 1'%61

(PB 151107 $2.00)149 Brazing ,c. !i•ih T.amperature Service. February 21, 1961 (P9 151108 $1.00)150 A Review of Beni.ing Methods for Stainles Steel Tubing, March 2, 1961 (PD 151109 41.511

Iit' Environmental and Mrtallurgical Fa.tco. of Stiess-Cormosson Cracking in lligh-.trenSth Steels. April 14. 1961(.-B 15 t110 $t,. ? n

152 Binary and remary Phase Diagrams of Cc:lumblum. Molybdentv. Tantalum. and Tungilen. April 28. 1961(AD 257730 33. 40)

153 Physical Metallur6y of Nickel-Base Superal!oys, May 5. 1961 (AD 253041 $1.2-5)154 Evolution of Ultrahsgh-Suength, Il•rdenablc Steels for Solid--Popeli•tl rf)x W.t-Motc Cases. May 2.. 1961

(A U 25791768S1. 25)155 f"'d.tion of Tungstrn. July 17. 1961156 Design lntormation on A1l-350 Stainless Steel for Aircraft and Missiles. July 28. 1961157 A Summary of the Theory of Fracture in Metals. August 7. 1961

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